assert: add rejects() and doesNotReject()

Implement asynchronous equivalent for assert.throws() and
assert.doesNotThrow().

PR-URL: https://github.com/nodejs/node/pull/18023
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 49 insertions, 15 deletions

diff --git a/lib/assert.js b/lib/assert.js
index f8eeba7222..b0d0d9ab4c 100644
--- a/lib/assert.js
+++ b/lib/assert.js
@@ -425,14 +425,23 @@ function getActual(block) {
   return NO_EXCEPTION_SENTINEL;
 }
 
-// Expected to throw an error.
-assert.throws = function throws(block, error, message) {
-  const actual = getActual(block);
+async function waitForActual(block) {
+  if (typeof block !== 'function') {
+    throw new ERR_INVALID_ARG_TYPE('block', 'Function', block);
+  }
+  try {
+    await block();
+  } catch (e) {
+    return e;
+  }
+  return NO_EXCEPTION_SENTINEL;
+}
 
+function expectsError(stackStartFn, actual, error, message) {
   if (typeof error === 'string') {
-    if (arguments.length === 3)
+    if (arguments.length === 4) {
       throw new ERR_INVALID_ARG_TYPE('error', ['Function', 'RegExp'], error);
-
+    }
     message = error;
     error = null;
   }
@@ -443,21 +452,21 @@ assert.throws = function throws(block, error, message) {
       details += ` (${error.name})`;
     }
     details += message ? `: ${message}` : '.';
+    const fnType = stackStartFn === rejects ? 'rejection' : 'exception';
     innerFail({
       actual,
       expected: error,
-      operator: 'throws',
-      message: `Missing expected exception${details}`,
-      stackStartFn: throws
+      operator: stackStartFn.name,
+      message: `Missing expected ${fnType}${details}`,
+      stackStartFn
     });
   }
   if (error && expectedException(actual, error, message) === false) {
     throw actual;
   }
-};
+}
 
-assert.doesNotThrow = function doesNotThrow(block, error, message) {
-  const actual = getActual(block);
+function expectsNoError(stackStartFn, actual, error, message) {
   if (actual === NO_EXCEPTION_SENTINEL)
     return;
 
@@ -468,16 +477,41 @@ assert.doesNotThrow = function doesNotThrow(block, error, message) {
 
   if (!error || expectedException(actual, error)) {
     const details = message ? `: ${message}` : '.';
+    const fnType = stackStartFn === doesNotReject ? 'rejection' : 'exception';
     innerFail({
       actual,
       expected: error,
-      operator: 'doesNotThrow',
-      message: `Got unwanted exception${details}\n${actual && actual.message}`,
-      stackStartFn: doesNotThrow
+      operator: stackStartFn.name,
+      message: `Got unwanted ${fnType}${details}\n${actual && actual.message}`,
+      stackStartFn
     });
   }
   throw actual;
-};
+}
+
+function throws(block, ...args) {
+  expectsError(throws, getActual(block), ...args);
+}
+
+assert.throws = throws;
+
+async function rejects(block, ...args) {
+  expectsError(rejects, await waitForActual(block), ...args);
+}
+
+assert.rejects = rejects;
+
+function doesNotThrow(block, ...args) {
+  expectsNoError(doesNotThrow, getActual(block), ...args);
+}
+
+assert.doesNotThrow = doesNotThrow;
+
+async function doesNotReject(block, ...args) {
+  expectsNoError(doesNotReject, await waitForActual(block), ...args);
+}
+
+assert.doesNotReject = doesNotReject;
 
 assert.ifError = function ifError(err) {
   if (err !== null && err !== undefined) {